Hardwood flooring generally consists of a number of juxtaposed elongated tongue-and-groove planks interlocked with each other, and then fastened in position to a subjacent subfloor. To fasten these hardwood planks to the subfloor of a room (composed for example of plywood plates and/or floor joists), it is known to use hardwood flooring nailers. Such nailers can either be manually or pneumatically operated.
Manually-operated nailers generally comprise a main body with a floor-engageable sole mounted to its bottom surface, upon which the tool rests against a hardwood plank prior to discharging a fastener in the latter. These nailers also comprise a magazine containing a frangible strip of collated metallic fasteners, such as L- or T-shaped barbed cleats or U-shaped staples, fed to a fastener discharge mechanism. A plunger having an impact-receiving head member at an outer free end thereof is slidably mounted to and extends out of the nailer's main body, and a recoil spring biases the plunger away from the nailer's main body into its extracted position where it is extended out of the nailer's main body. The fastener discharge mechanism is activated when the plunger's head member is struck with a mallet to cause the plunger to slidably retract inside the nailer's main body to impact on a selected fastener of the fastener strip and drive this fastener out of the nailer and into the subjacent workpiece. The fastener is fully driven into the workpiece only if the plunger has been struck hard enough so as to have retracted inside the nailer's main body up to a determined retracted limit position.
After the plunger is struck, the recoil spring is used to resiliently bias the plunger head back to its initial extracted position.
In using the above described manual nailing machines, problems occur if the user does not strike the plunger with enough force to retract the plunger up to its retracted limit position in which the fastener is fully driven into the workpiece. For instance, to drive a partially driven fastener the rest of the way into the workpiece, the user must again apply enough force to the plunger head to recompress the recoil spring. Accordingly, recompressing the recoil spring several times over the course of a flooring job can cause the workman to become prematurely exhausted.
Furthermore, weaker users who are unable to retract the plunger all the way to its retracted limit position with a single mallet blow may not be able to use the nailer at all.
To remedy this problem, certain prior art nailers are provided with a ratchet mechanism holding the plunger in intermediate positions after it is struck with a mallet, until the plunger reaches its retracted limit position, at which point the ratchet mechanism is released and the recoil spring is allowed to urge the plunger back to its rest or neutral position. This feature gives the user the opportunity to strike multiple mallet blows on the plunger head member to gradually move towards the retracted limit position, in which the fastener has been driven completely into the workpiece. However, existing ratchet-provided nailers have been found to wear out or break too rapidly.